Lake boundary is also partial town boundary. How to add the town?

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Hello, on the Internet (ie Google) the CDP “Oak Trail Shores” (OTS) can be found. It is a CDP. I also think of it as a hamlet. We have a town hall and a fire dept.

I have tried in vain to find a shape file for OTS. But it does seem to exist. Google knows the shape, as does: Oak Trail Shores Texas Street Map 4853212

So I have decided to manually add the admin boundary for the CDP (admin level 8).

My question: A large portion of the eastern boundary already exists in OSM as a reservoir (https://www.openstreetmap.org/edit#map=16/32.48698/-97.81928), aka Lake Granbury.

Can a way be part of a reservoir and a CDP? I have done basic edits in OSM, i.e. adding streets and correcting streets. But a whole admin boundary is new to me, so I just want to approach the task correctly.

Any advice will be appreciated.

Thank you in advance,
Eric W

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Cut the boundary of the lake in pieces where it is the same as the boundary from the village and place that part in the relation of the village boundary.

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So when the boundary of the lake changes, does also the boundary of the admin area change?

It is relevant whether the border has been defined once along the shoreline of the lake or if the border literally is the shoreline. Depending on the answer to that, the boundary should either be drawn as a separate way (that aligns with the shoreline) or as actually-the-shoreline.
From a technical viewpoint, both can be done.

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Just to avoid confusion: the word “hamlet” has a specific meaning in OSM. You can apply the place=hamlet tag to any place of a certain relative size and importance; it doesn’t need to be incorporated as such. That’s good news for you, since Texas doesn’t have an official notion of a hamlet. So this place node is probably already correctly tagged.

However, OSM does distinguish between administrative boundaries and other boundaries. The “boundary” of a census-designated place is not an administrative boundary, even if it happens to align with special district boundaries (school, fire, etc.). Rather, the CDP boundary should be tagged as boundary=census to emphasize its ephemeral nature. If Oak Trail Shores happens to have a definite boundary despite being unincorporated, consider additionally mapping a landuse=residential area or boundary=place relation by that name.

All these things can overlap and intersect. In general, there are some differences of opinion about whether you should cut apart areas and use multipolygons or whether you should connect the different kinds of features together. Since this is your first boundary, I’d suggest playing it safe: draw the CDP or place boundary as a separate feature. You could either eyeball an alignment with the reservoir (less tedious) or try to connect it to the reservoir (if you’re certain it extends to the edge of the water by definition). Forming a multipolygon with the reservoir is more complex and difficult to do in the Web-based iD editor, but perhaps someone else could explain how to do it step by step if you’re interested.

For more information about place classification and boundaries in OSM, consult the U.S. documentation on this subject.

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However, we can’t copy anything from any form of Google map product, & the Landsat page also appears to say Copyright?

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Heh, yes, that site is literally selling screenshots of ArcGIS online basemaps, definitely under copyright. The Census Bureau is the authority on CDPs (says it in the name) and includes their boundaries in TIGER, which is in the public domain. You can load TIGER boundaries as a custom background layer using the following template:

https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/tigerWMS_Current/MapServer/export?dpi=96&transparent=true&format=png32&layers=show:20,21,24,25,26,27,28,29,30,31,34,35,36,37,40,41,42,43,44,45,46,47,48,49,50,51,52,53,80,81,82,83&bbox={bbox}&bboxSR={proj}&imageSR=102100&size={width},{height}&f=image

Note that, although it is literally the source for CDP boundary data, TIGER has a tendency to hallucinate a bit. You’ll occasionally see bizarre jogs and rough edges, even if it’s pretty obvious that it’s trying to follow a road. You might want to apply some common sense.

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I hope this is replying to all the responses I received. I want to start by saying thank you. This is great info, and a lot to digest… Which I plan to do.

I will take everything into consideration, before making any additions.

I’ll post back, and mark a solution when I find the correct fit for this task.

Thank you again,
Eric

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It is my understanding that the lake boundary is defined by the Brazos River Authority (BRA), so regardless of lake level the boundary remains the same. The BRA even has an easement for the lake, that is defined by a certain height above sea level. There is one for the actual lake reservoir, and one elevation that restricts building within a certain distance of the lake.